On 12/3/21 10:45 PM, Jens Axboe wrote:
If we have a list of requests in our plug list, send it to the driver in
one go, if possible. The driver must set mq_ops->queue_rqs() to support
this, if not the usual one-by-one path is used.
Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
---
block/blk-mq.c | 24 +++++++++++++++++++++---
include/linux/blk-mq.h | 8 ++++++++
2 files changed, 29 insertions(+), 3 deletions(-)
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 22ec21aa0c22..9ac9174a2ba4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -2513,6 +2513,7 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
{
struct blk_mq_hw_ctx *this_hctx;
struct blk_mq_ctx *this_ctx;
+ struct request *rq;
unsigned int depth;
LIST_HEAD(list);
@@ -2521,7 +2522,26 @@ void blk_mq_flush_plug_list(struct blk_plug *plug, bool from_schedule)
plug->rq_count = 0;
if (!plug->multiple_queues && !plug->has_elevator && !from_schedule) {
- blk_mq_run_dispatch_ops(plug->mq_list->q,
+ struct request_queue *q;
+
+ rq = plug->mq_list;
+ q = rq->q;
+
+ /*
+ * Peek first request and see if we have a ->queue_rqs() hook.
+ * If we do, we can dispatch the whole plug list in one go. We
+ * already know at this point that all requests belong to the
+ * same queue, caller must ensure that's the case.
+ */
+ if (q->mq_ops->queue_rqs &&
+ !(rq->mq_hctx->flags & BLK_MQ_F_TAG_QUEUE_SHARED)) {
What is the dependency on shared tags here?
From what I've seen it's just about submitting requests; the only
difference to shared tags is the way the tags are allocated.
Care to explain?
Cheers,
Hannes
--
Dr. Hannes Reinecke Kernel Storage Architect
hare@xxxxxxx +49 911 74053 688
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